<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
	<script type="text/javascript">
		
		var i = 1;
		var sum = 0;
		do{
			sum+=i;
			i++;
		}while(i<=i+1);
		document.write("1+2+...+n="+sum);
	</script>
		
	</body>
</html>
